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<h3>Hypertext Help with LaTeX</h3>

<h2>LaTeX 2.09 and LaTeX2e</h2>

<p>The following information is excerpted from "A Document
    Preparation System: LaTeX" by Leslie Lamport, 2nd edition and/or
    "LaTeX2e for authors", by the LaTeX3 Project Team, June 1994.</p>

<p>LaTex2e was produced in an attempt to reconcile the various,
    sometimes incompatble, "flavors" of LaTeX which were developing.
    Some of these included the New Font Selection Scheme (NFSS),
    SLITeX (for slides), AASTeX (the American Astronomical Society
    macros), etc. The major change to LaTeX2e is the method for
    trying to make the use of add-on packages more uniform by the
    introduction of "classes" and "packages." Most of the new
    commands are the "initial" commands, i.e., those which can
    appear only <em>before</em> the <tt>\documentclass</tt>
    command.</p>

<p>A few standard LaTeX commands have been modified and a few
    new commands added, notably:</p>

<ul>
    <li><tt><a href="ltx-18.html">\newcommand</a></tt> (and related)
        commands, which now allow for an optional argument in newly
        defined commands
    </li>
    <li><tt><a href="ensuremath.html">\ensuremath</a></tt></li>
</ul>


<h3>Document Styles and Style Options</h3>

<p>In LaTeX2e, documents begin with a <tt>\documentclass</tt>
    command. This replaces the LaTeX 2.09
    <tt><a href="ltx-22.html">\documentstyle</a></tt> command. The
    <tt>\usepackage</tt> command has been added and is used in
    conjunction with <tt>\documentclass</tt>.</p>

<p>aTeX2e still understands the old
    <tt><a href="ltx-22.html">\documentstyle</a></tt> command; if it
    is encountered, LaTex2e enters <em>compatibility mode</em> in
    which most 2.09 input files should still be processed properly.</p>


<h3>Type Styles and Sizes</h3>

<p>LaTeX 2.09 commands for changing type style, for example,
    <tt>\tt</tt>, still work similarly in LaTeX2e. The major
    difference is that <tt>\sc</tt> and <tt>\sl</tt> can no longer
    be used in math mode (except when LaTeX2e is in
    <em>compatibility mode</em>, see above).</p>

<p>However, <a href="fonts2e.html">a new set of commands</a>
    have been added to allow separate (and independent)
    specification of</p>

<ul>
    <li>Shape</li>
    <li>Series</li>
    <li>Family</li>
</ul>

<p>These can be combined to form a wide variety of type styles. If a style
    you specify is not available on your computer, LaTeX2e produce a warning
    message and will substitute a style it thinks is similar.</p>

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<address>
    Revised 14 May 1995.
</address>


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